For the last couple of years around the 'Fourth', PBS has been airing a documentary about an Italian-American family whose members for many generations, have been manufacturing the fireworks, constructing the apparatus, and managing the ignition of massive pyrotechnic displays to celebrate different events across the U.S., and some of the rules and regulations that the differing municipalities require them to follow are almost mind-boggling in their complexity. The video covered a display being set up in D.C., and it went through the safety regulations this company had to adhere to in order for the fire department officials to OK the show: All the devices had to be ignited from a barge floating on a body of water, the barge had to be X number of feet away from any spectators, barge had to be X number of feet away from any structure or buildings, they had to fire rockets and bombs point blank at the proposed distance the crowds would be at to ensure that in the event of a mishap no firework could reach anyone in the audience, etc., etc..
Now there's a whole world of difference when you watch some of these YouTube videos of mascleta displays in Espana, holy smoke, the fire marshals in Spain must be a really laid back group of folks. In some of the vids I watched it seemed like the streets were so narrow that if you stood in the middle of one and stretched out your arms that you could touch the buildings on both sides with your fingertips, and yet there they are with fireworks hangind from strings going all the way down the block; unbelievable.